1. Field of the Invention
The invention relates to a comparator for determining the relative size of flaws or cracks in a structural member based on a liquid penetrant placed in the flaws.
2. Description of the Prior Art
In the inspection of structural parts such as aircraft parts a fluorescent liquid penetrant is painted on the surface to allow the penetrant to seep in any flaws or cracks. The penetrant is washed off the surface with hot water; the surface dried; and the structure is placed under black light to allow any penetrant in discontinuities to fluoresce for location of the discontinuities. Comparators have been used to determine the size of discontinuities and spacing between adjacent discontinuities and to determine if the discontinuities are round (porosity) or linear (cracks). One known comparator is a flat transparent member having spots of material of different sizes that fluoresce in the presence of blacklight. The prior device however is hard to use and does not provide the quality measurements desired to determine if the part should be reworked to remove the discontinuities or the part rejected. In this respect, the spots of the prior art device are only an approximation of actual size.
A comparator is desired in order to allow quick quality measurements to be made of the size of the discontinuities in the surface, the distance between adjacent discontinuities and whether the discontinuities are round (porosity) or linear (cracks) and the dimensions thereof.